Officers say the incident took place at Queen’s Park between 7pm and 7.30pm on Tuesday, May 3, in the area around the main bandstand.
A group of teenage boys are alleged to have thrown items at the man, shouted abuse, spat at him and punched him.
A Derbyshire police spokesperson said: “The man has suffered cuts and bruising to his eye and face.
“It is believed the boys were around 16 years old or older and were wearing tracksuits.
“Were you in the Queen’s Park area around that time? Do you have any information which could help?
“If you can help please contact us on the non-emergency details below, quoting reference 22000252404.”
Facebook – send a private message to the force’s Facebook page
Twitter – direct message @DerPolContact
Website – use the online contact form
Phone – call 101
Contact Crimestoppers on 0800 555 111.